Mechanisms Behind Tailing in the Pressure Inactivation Curve of a Clinical Isolate of Escherichia Coli O157:H7

Int J Food Microbiol. 2006 May 25;109(1-2):103-8. doi: 10.1016/j.ijfoodmicro.2006.01.018. Epub 2006 Feb 24.

Abstract

The tailing in pressure inactivation curve of clinically isolated Escherichia coli O157:H7 was investigated. A typical tailing was observed after the treatment period for 30min when 10(7) CFU/ml of the cell suspension was subjected to pressure treatment at 300MPa and 25 degrees Celsius. There was no effect on the tailing profiles by the addition of pressure-killed cells and released cellular components. When cells survived at a tail portion were re-propagated (tail-culture) and subjected to second pressure treatment, the cells of the tail-culture exhibited eminently higher barotolerance compared to those of the original-culture, suggesting that the presence of genetically pressure-resistant subpopulation was responsible for the tailing. The cytoplasmic membrane of the tail-culture cells had higher stability to a pressure treatment at 100MPa for 10min than that of the original-culture, which was evidenced by lower permeability to ethidium bromide. The addition of non-ionic surfactants including 0.5microl/ml polyoxyethylene p-t-octylphenyl ester (Triton X-100) and 0.53mg/ml lauric sugar ester dramatically reduced the level of tailing and made the inactivation curve linear.

MeSH terms

  • Colony Count, Microbial
  • Emulsifying Agents / pharmacology*
  • Escherichia coli O157 / drug effects
  • Escherichia coli O157 / growth & development*
  • Hydrostatic Pressure*
  • Kinetics
  • Lauric Acids / pharmacology
  • Models, Biological*
  • Octoxynol / pharmacology
  • Surface-Active Agents / pharmacology*
  • Temperature
  • Time Factors

Substances

  • Emulsifying Agents
  • Lauric Acids
  • Surface-Active Agents
  • Octoxynol